1. Field of the Invention
The invention relates to a process and an apparatus for the production of an ingot, which can have a solid or a hollow shape, by spraying a molten metal by use of a pressurized gas and catching the spray particles on a catching surface. The ingot is formed as a continuous agglomerate of the spray particles. As a semifinished product, such an ingot is further processed into wires, tubes or other shapes.
2. Related Art
Ingots are normally produced by pouring into ingot molds and subsequent rolling or by continuous casting.
According to a process known from DE-PS No. 22 52 139, molded articles, e.g., flat disks for forgings are produced by spraying molten metal by used of pressurized gas and collecting the spray particles on a form. The process has special advantages because segregations and casting structures are avoided in the production preforms and therefore difficult alloys can be processed into formed pieces. This procedure in most cases permits a reduction in the number of forming stages necessary to produce the ultimate product in comparison with conventional production methods.
Production of ingots, e.g., for the production of tubes, by catching the spray particles on a cylindrical form has already been proposed. In the spray process thus far known, however, the producible ingot length has been greatly limited because with greater lengths the distance of the catching surface from the spray nozzle during the spray process changes too greatly and the conditions for the flow of the spray gas and for cooling the spray particles become too unfavorable. Therefore ingots whose length is at least twice that of its characteristic cross-sectional dimension (e.g., diameter or diagonal) cannot, or can only conditionally, be produced according to this known process.
Also known is the production of hollow cylinders, e.g., in the form of thick-walled hollow ingots as semifinished products (rough-pierced tube blanks) for tube production with varying wall thicknesses by spraying molten metal in small droplets and catching the spray particles on a rotatable cylindrical mandrel that can be shifted in its longitudinal direction (GS-PS No. 1 599 392). The thickness of the sprayed-on layer, i.e., the wall thickness of the resulting hollow cylinder depends on the amount of the molten metal sprayed per unit of time and on the speed of the rotary and longitudinal movement of the mandrel. The relative thickness of the sprayed-on layer can amount to 100% of the entire thickness of the final product but may also be smaller. The hollow cylinders thus produced are suitable for hot working (e.g., extrusion) or--with full thickness--directly for cold working (e.g., cold pilger rolling). Compared to the usuaul process, this process offers especially the following advantages over casing:
1. No segregation or separations,
2. Fewer forming steps required (energy and material saving),
3. No casting structure (better deformation), and
4. Production of "exotic" alloys is possible.
However, this known spary process has one significant disadvantage: the rotatable mandrel that can be moved longitudinally must have a surface to which the sprayed-on particles adhere, so that they do not fall of the mandrel during the rotation. But as a result of this, following the spray process, the mandrel cannot be pulled out of the formed hollow cylinder which, moreover has shrunk on during cooling. If the mandrel consists of a brittle material, e.g., ceramic, it must be crushed and its fragments must be completely removed, which entails considerable expense.
If the mandrel is made, e.g., of sheet steel, there is the danger that it will be deformed by the high temperature of the resulting molten metal particles. In this case, too, its mandatory removal prior to the finishing process is a costly matter.